Pleurosigma
Pronunciation : Pleu`ro*sig"ma
Part of Speech : n.
Etymology : [NL. See Pleuro-, and Sigma.] (Bot.)
Definition : Defn: A genus of diatoms of elongated elliptical shape, but having the sides slightly curved in the form of a letter S. Pleurosigma angulatum has very fine striations, and is a favorite object for testing the high powers of microscopes.
Source : Webster's Unabridged Dictionary, 1913